A system has been known which is capable of synchronizing time between a plurality of apparatuses with high accuracy. In the system, each of the plurality of apparatuses synchronizes time with the clock of a time server, thereby checking the measurement time thereof. In the system, for example, as a method of improving the operation rate of the system, the time servers are redundantly provided.
When the time servers are redundantly provided, the structure of a system for synchronizing the time between a plurality of time servers becomes complicated.